Sandy mudstone water content control device based on positive and negative pressure principle

Abstract

The invention provides a sandy mudstone water content control device based on a positive and negative pressure principle. The sandy mudstone water content control device comprises a wide-temperature-zone constant-temperature box, a temperature control device and a water content regulation and control unit, during working, firstly, the intelligent temperature control device is used for adjusting a proper temperature to air-dry the sandy mudstone until the gravity transmitted by the electronic gravity sensor does not change any more; on one hand, the intelligent humidifier and the rotating wheel type vacuum pump are started through external remote control, so that water vapor reaches the positive pressure cabin from the negative pressure cabin through sandy mudstone pores in the sample fixing table under the action of positive and negative pressure, and the water content of the sandy mudstone begins to increase; on the other hand, the electronic gravity sensor transmits real-time data, and the water content and the rate of the sandy mudstone sample are calculated according to a set formula program; and meanwhile, when the water content of the sandy mudstone sample reaches a set value of a required test, the program automatically stops, and the wide-temperature-zone constant-temperature box recovers to a normal state.

Description

Technical Field

[0001] The invention relates to the technical field of sandy mudstone water content control test, and in particular to a sandy mudstone water content control device based on the positive and negative pressure principle. Background Art

[0002] Water content is one of the important factors affecting the physical and mechanical properties of sandy mudstone. Sandy mudstone is a rock composed of clay minerals and detrital minerals. It has a high content of hydrophilic clay minerals, such as montmorillonite, which makes sandy mudstone have significant water absorption and expansion properties. In the field of geotechnical engineering, the change of water content of sandy mudstone has a huge impact on its mechanical properties and is one of the important factors leading to engineering accidents. In slope engineering, the change of water content of sandy mudstone will affect its shear strength. When the water content increases, the shear strength decreases, which is easy to cause geological disasters such as slope instability and landslides, posing a serious threat to engineering construction and the surrounding environment. The traditional "soak-dry" method exposes serious limitations when processing sandy mudstone. During soaking, a large amount of water flows into the pores, and clay minerals such as montmorillonite swell when exposed to water, causing changes in the internal structural stress of the rock. During the drying process, water dissipates rapidly and the minerals shrink. This drastic volume change makes the sandy mudstone extremely prone to disintegration, seriously damaging its original structure, making it impossible to accurately obtain its true physical and mechanical properties data at different water contents, which greatly affects the research and evaluation of sandy mudstone in engineering applications.

[0003] The commonly used experimental instruments for controlling the moisture content of sandy mudstone on the market are mainly drying ovens, rapid moisture meters, high-frequency moisture detectors, capacitive sensor moisture meters, etc.

[0004] Key issue ①: The traditional oven drying test for moisture content only considers that high temperature can dry sandy mudstone, but does not consider the precise temperature for drying. If the temperature is too high, some of the bound water in the sandy mudstone may escape prematurely, making the measured moisture content too high. If the temperature is too low, the drying time may be too long, or even incomplete drying.

[0005] Key question ②: Different types of sandy mudstones, such as montmorillonite sandy mudstone and kaolinite sandy mudstone, have different mineral compositions, particle sizes, pore structures, etc., which will affect the existence form (such as adsorbed water, bound water, free water) and content of water. For example, montmorillonite sandy mudstone has strong water absorption and swelling properties, and its water content and distribution law are significantly different from those of kaolinite sandy mudstone. These characteristics need to be considered when measuring water content.

[0006] Key issue ③: The size and shape of the sample will affect the speed and uniformity of water evaporation. The water inside a larger sample evaporates relatively slowly, and a longer drying time or a stronger detection signal may be required to accurately measure the moisture content. Irregularly shaped samples may cause uneven instrument detection. For example, when using a capacitive sensor moisture meter, the irregular shape may cause uneven electric field distribution, affecting the measurement of the dielectric constant.

[0007] Key issue ④: Most of these instruments perform measurements in a relatively stable laboratory environment, and rarely consider the complex working conditions of sandy mudstone in actual engineering environments, such as dry-wet cycles, freeze-thaw cycles, positive and negative pressure changes, etc.

[0008] CN 119086878 A: A device for testing the hydrological properties of rock and soil samples under dry-wet cycles and a method for using the device; the whole process of dry-wet cycles and monitoring is automatically carried out through an electric control system, reducing the influence of manual intervention on the test accuracy, and the dry-wet cycle system can better simulate the dry-wet alternation phenomenon in nature. The technical solution can be applied to the precise testing of a single sandy mudstone under dry-wet cycle conditions, but it cannot measure the simulation of multiple sandy mudstones under complex working conditions such as dry-wet cycles, freeze-thaw cycles, temperature, positive and negative pressure, etc.

[0009] CN 107782640 A:A method for detecting water uniformity of rock specimens and calculating diffusion coefficients based on digital images. The method introduces digital image technology into the detection of water uniformity of rock specimens and the calculation of diffusion coefficients. By acquiring a color difference image of the sample surface during humidity diffusion, MATLAB is used to identify and extract color grayscale values ​​and calculate variance to analyze water uniformity, thereby achieving a quantitative description of rock water distribution. The method can not only determine water uniformity, but also establish a quantitative relationship through regression analysis of pixel grayscale values ​​and water content. However, for sandy mudstone, which has extremely small pores or special water absorption, the water uniformity may not be effectively detected.

[0010] CN 212159647 U: A device for monitoring the change characteristics of rock water content under rainfall conditions; the resistivity of rock samples is measured by a digital bridge, a conversion device and electrodes, and data processing is performed with the aid of a computer, so that the information on the change of rock water content can be obtained in real time during the rainfall simulation process, but accurate data cannot be measured for the water content of some sandy mudstones, and there are errors in the determination of the water content of sandy mudstones. Summary of the invention

[0011] The purpose of the present invention is to provide a sandy mudstone moisture content control device based on the positive and negative pressure principle, which can effectively control the moisture content and rate of sandy mudstone. In order to achieve the above technical features, the purpose of the present invention is achieved as follows:

[0012] A device for controlling the moisture content of sandy mudstone based on the principle of positive and negative pressure, comprising a wide temperature range constant temperature box and a temperature control device;

[0013] A moisture content control unit is installed in the wide temperature range constant temperature box, and the moisture content control unit includes a sample fixing table, and a mounting groove adapted to the shape of the sandy mudstone sample is provided on the sample fixing table, and the mounting groove is respectively connected with the positive pressure cabin and the negative pressure cabin provided on both sides of the sample fixing table, the positive pressure cabin is connected to the mist outlet of the humidifier, and the negative pressure cabin is connected to the air inlet of the vacuum pump, and the sample fixing table, the positive pressure cabin and the negative pressure cabin are provided with a sealing cover plate on the top, and an electronic gravity sensor is provided under the sample fixing table, and the electronic gravity sensor is connected to the calculation and data processing unit;

[0014] The temperature control device is installed on the wide temperature range constant temperature box and is used to adjust the temperature inside the wide temperature range constant temperature box.

[0015] The positive pressure cabin and the negative pressure cabin are respectively connected to the mist outlet of the humidifier and the air inlet of the vacuum pump through a pressure stabilizing balance port.

[0016] The air inlet of the vacuum pump is provided with an air stop valve.

[0017] The wide temperature range constant temperature box is provided with a temperature lock cover, and the temperature lock cover is provided with a handle for convenient opening and closing.

[0018] A support platform is arranged at the bottom of the wide temperature range constant temperature box, a buffer layer is arranged on the top of the support platform, and the electronic gravity sensor is installed on the top of the buffer layer.

[0019] A method for using a sandy mudstone moisture content control device based on the positive and negative pressure principle comprises the following steps:

[0020] S1: Install the moisture content control unit in the wide temperature range constant temperature box;

[0021] S2: Check the air tightness of each component of the moisture content control unit, and check whether the temperature control device, electronic gravity sensor, humidifier and rotary vacuum pump are working properly;

[0022] S3: Open the wide temperature range thermostat and place the sandy mudstone sample in the mounting groove on the sample fixing table;

[0023] S4: According to different working conditions of sandy mudstone, the wide temperature range constant temperature box is closed, and the temperature in the wide temperature range constant temperature box is adjusted by the temperature control device. The electronic gravity sensor is connected to the calculation and data processing unit to collect and transmit sandy mudstone data, and the initial mass of the sandy mudstone is recorded as m;

[0024] S5: The temperature in the wide temperature range constant temperature box is controlled at room temperature by a temperature control device, and the sandy mudstone on the sample fixing table is air-dried until the data recorded by the electronic gravity sensor does not change, that is, the sandy mudstone has been completely air-dried, and its mass is recorded as m0. The humidifier and vacuum pump are started to allow water vapor to enter the negative pressure chamber from the positive pressure chamber through the pores of the sandy mudstone in the sample fixing table, so that the water content of the sandy mudstone increases. After positive pressure humidification, negative pressure assisted water vapor penetration and other operations, the total mass of the sandy mudstone and the water contained inside at a certain moment is m t , the mass of water mw = m t -m0, the moisture content ω is calculated as:

[0025]

[0026] The initial gravity G0 of the sandy mudstone sample was measured by an electronic gravity sensor before the experiment. According to the gravity calculation formula G = mg, we can get At a certain measurement moment after the positive and negative pressure and humidification process are completed, the electronic gravity sensor measures the total gravity G of the sandy mudstone and the water contained in it. t , we can get mt = Gt / g, and replace m0 and m t Substituting the expression into the moisture content calculation formula, we can get:

[0027]

[0028] In this way, the real-time measurement data of the electronic gravity sensor, the computing and data processing unit are directly used to calculate the water content and rate of the sandy mudstone at different stages in real time.

[0029] Assume that ω1 is the water content of sandy mudstone at time t1, and ω2 is the water content of sandy mudstone at time t2, then:

[0030]

[0031] The rate of change of moisture content v can be expressed as:

[0032]

[0033] Substituting the expressions of ω1 and ω2 into the equation, we get:

[0034]

[0035] After simplification, we get:

[0036]

[0037] Measured by gravity sensor, let G0 be the gravity corresponding to the dry weight of sandy mudstone, G t1 is the total gravity of sandy mudstone and the water contained in it at that moment, Gt2 is the total gravity of sandy mudstone and the water contained inside at the moment, then the expression of water content change rate v is:

[0038]

[0039] A method for controlling the moisture content and its changing rate of a sandy mudstone moisture content control device based on the positive and negative pressure principle comprises the following steps:

[0040] By adjusting the humidification amount of the humidifier and the pressure in the positive pressure chamber, the amount of water vapor entering the pores of the sandy mudstone can be accurately controlled. According to the pore structure and target moisture content of the sandy mudstone, the working power of the humidifier and the pressure value of the positive pressure chamber are set. For sandy mudstone with smaller pores, the humidification amount is appropriately reduced and the positive pressure is increased, so that water vapor can slowly and fully penetrate into the pores, avoiding pore blockage or uneven moisture distribution caused by excessive and rapid water vapor.

[0041] The water absorption curves of different types of sandy mudstone under different positive pressures and humidification amounts are determined through preliminary experiments. Based on this, the positive pressure humidification process is accurately controlled in the formal experiment, thereby achieving effective control of the increase in water content. The air inlet of the vacuum pump is connected to the negative pressure chamber. By adjusting the vacuum pump's pumping rate and the pressure in the negative pressure chamber, the migration speed and discharge volume of water vapor in the sandy mudstone are controlled. When it is necessary to accelerate water penetration, the vacuum pump's pumping power is increased to enhance the negative pressure effect, so that water can flow from the positive pressure chamber to the negative pressure chamber faster through the pores of the sandy mudstone driven by the pressure difference, ensuring that the rock is fully moistened and the water is evenly distributed, while avoiding water residue, and improving the accuracy and completeness of water content measurement.

[0042] The wide temperature range thermostat is connected to an external temperature control device to accurately control the temperature at different stages. In the air-drying stage, the temperature is controlled in an appropriate range slightly higher than the room temperature to accelerate the evaporation of water, so that the sandy mudstone can reach a completely air-dried state as soon as possible and accurately obtain the dry weight m0. In the stage of increasing the water content, the appropriate temperature is selected according to the characteristics of the sandy mudstone and the target water content. For some sandy mudstones with enhanced water absorption at higher temperatures, the temperature can be appropriately increased to promote water absorption, but it is necessary to avoid excessively high temperatures that may cause changes in the internal structure or mineral composition of the rock. Through precise temperature regulation and auxiliary positive and negative pressure effects, effective control of the water content can be achieved.

[0043] The electronic gravity sensor under the sample fixing table monitors the mass change of sandy mudstone in real time and transmits it to the calculation and data processing unit. During the experiment, the real-time water content ω and the change rate of water content v are calculated according to the gravity change, and the gravity data is recorded at a certain time interval. Once it is found that the change rate of water content deviates from the expected range, the positive pressure, negative pressure or temperature and other parameters can be adjusted in time; when the calculated water content or the change rate of water content does not match the preset value, the system automatically adjusts the working parameters of the humidifier, vacuum pump or temperature control device; if the water content increases too fast, reduce the humidification amount of the humidifier or reduce the pressure of the positive pressure cabin; if the water content increases too slowly, appropriately increase the vacuum pump exhaust power or increase the temperature.

[0044] The present invention has the following beneficial effects:

[0045] 1. The device of the present invention uses a temperature control device to accurately control the temperature in the wide temperature range constant temperature box, providing a stable and precisely controllable temperature condition in the wide temperature range constant temperature box, ensuring that the rock sample is in a set temperature environment during the experiment. When studying the changing characteristics of rock moisture content, different temperatures will significantly affect the evaporation and diffusion rate of water and the physical and chemical properties of rocks. Through precise temperature control, the interference of temperature fluctuations on the test results can be eliminated, allowing researchers to accurately explore the laws of interaction between rocks and water at specific temperatures, and improve the accuracy and reliability of experimental data.

[0046] 2. The device of the present invention adopts the principle of positive and negative pressure to allow water vapor to quickly enter the pores of sandy mudstone, thereby increasing the water content of sandy mudstone and reaching the water content required for the predetermined test. Under the action of positive pressure, water can more effectively penetrate into the pores and cracks of the rock, ensuring that the interior of the rock is fully moistened, so that the water content measurement results can better reflect the actual water absorption of the rock. Negative pressure helps to accelerate the discharge of water inside the rock, promote the rapid migration and diffusion of water in the rock, avoid residual water, and thus improve the accuracy and completeness of the water content measurement. For example, in the process of simulating the infiltration of rock by reservoir water in the drawdown zone of the slope, positive pressure can simulate water pressure to push water deep into the rock; when studying the drainage characteristics of the rock, negative pressure can simulate the suction force in the natural drainage or evaporation process to fully discharge the water.

[0047] 3. The device of the present invention realizes precise control of the water content and its changing rate through real-time monitoring and feedback adjustment mechanism, ensuring that the water content of sandy mudstone changes at a predetermined rate to meet the test or engineering requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0049] Figure 1 A schematic diagram of the appearance structure of a sandy mudstone moisture content control device based on the positive and negative pressure principle provided in an embodiment of the present invention;

[0050] Figure 2 An internal structure diagram of a sandy mudstone moisture content control device based on the positive and negative pressure principle provided by an embodiment of the present invention;

[0051] Figure 3 A front view of the installation structure of the positive pressure cabin, negative pressure cabin, and electronic gravity sensor provided in an embodiment of the present invention;

[0052] Figure 4 A top view of the installation structure of the positive pressure cabin, negative pressure cabin, and electronic gravity sensor provided in an embodiment of the present invention;

[0053] Figure 5 A state diagram of a sandy mudstone sample being placed with the sealing cover plate opened according to an embodiment of the present invention;

[0054] Figure 6 A schematic diagram of the structure of a vacuum pump provided in an embodiment of the present invention;

[0055] In the figure: a wide temperature range constant temperature box 1, a temperature control device 2, a temperature lock cover 3, a handle 4, a sample fixing table 5, a positive pressure chamber 6, a negative pressure chamber 7, a pressure balancing port 8, an electronic gravity sensor 9, a gravity sensing protection cabin 10, a shock absorbing pad 11, a humidifier 12, an electromechanical equipment protection pad 13, a vacuum pump 14, a vacuum pump rotor 15, an air inlet 16, an air outlet 17, an air stop valve 18, a bracket 19, a sealing cover 20, and a sandy mudstone sample 21. DETAILED DESCRIPTION

[0056] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0057] In order to realize the above-mentioned technical features, the purpose of the present invention is achieved as follows:

[0058] See also Figure 1-6 , a sandy mudstone moisture content control device based on the positive and negative pressure principle, comprising a wide temperature range constant temperature box 1 and a temperature control device 2; a moisture content control unit is installed in the wide temperature range constant temperature box 1, and the moisture content control unit comprises a sample fixing table 5, and a mounting groove 5a adapted to the shape of the sandy mudstone sample 21 is provided on the sample fixing table 5, and the mounting groove 5a is respectively connected with the positive pressure cabin 6 and the negative pressure cabin 7 provided on both sides of the sample fixing table 5, the positive pressure cabin 6 is connected with the mist outlet of the humidifier 12, and the negative pressure cabin 7 is connected with the air inlet 16 of the vacuum pump 14, and a sealing cover plate 20 is provided on the top of the sample fixing table 5, the positive pressure cabin 6 and the negative pressure cabin 7, and an electronic gravity sensor 9 is provided under the sample fixing table 5, and the electronic gravity sensor 9 is connected with the calculation and data processing unit; the temperature control device 2 is installed on the wide temperature range constant temperature box 1, and is used to adjust the temperature in the wide temperature range constant temperature box 1.

[0059] The sandy mudstone moisture content control device provided in this embodiment has a mounting groove 5a adapted to the shape of the sandy mudstone sample 21 on the sample fixing table 5, so that the sandy mudstone sample can be accurately placed to keep a stable position during the experiment, play a role in locking and positioning, and avoid affecting the experimental results due to shaking or displacement. Figure 4 , Figure 5 ; Secondly, the mounting groove 5a is respectively connected with the positive pressure chamber 6 and the negative pressure chamber 7 provided on both sides of the sample fixing platform 5, and the sealing cover plate 20 serves as a sealing component to cover the sample fixing platform 5, the positive pressure chamber 6 and the negative pressure chamber 7 completely to prevent water vapor leakage. When the system is running, the gas in the positive pressure chamber 6 can be evenly distributed inside the mounting groove 5a on the sample fixing platform 5, thereby ensuring that the gas of the entire system only flows in an orderly manner through the positive pressure chamber 6, the mounting groove 5a and the negative pressure chamber 7 as channels during the positive and negative pressure operations of the entire system, thereby maintaining the sealing and pressure stability of the system and forming a complete gas passage. When working, firstly, water is supplied to the humidifier 12 to a predetermined water level through the water supply unit, the air tightness of the positive pressure chamber 6, the negative pressure chamber 7 and the outside is checked, and the sandy mudstone sample is placed in the installation slot 5a; then, the temperature lock cover 3 of the wide temperature range constant temperature box 1 is closed, and the program is started to control the temperature control device 2, and the temperature in the wide temperature range constant temperature box 1 is controlled at a suitable temperature, so that the sandy mudstone is air-dried or dried, and then the electronic gravity sensor 9 is transmitted to the calculation and data processing unit for calculation, and the dry weight and natural water content of the sandy mudstone are recorded; then , the temperature in the wide temperature range constant temperature box 1 is adjusted to room temperature through the temperature control device 2, the humidifier 12 and the vacuum pump 14 are started, and according to the principle of positive and negative pressure, the water vapor is passed from the positive pressure chamber 6 through the sandy mudstone pores in the sample fixing table 5 to the negative pressure chamber 7, thereby increasing the water content of the sandy mudstone; finally, according to the gravity conditions of the sandy mudstone at each stage transmitted to the operation unit by the electronic gravity sensor 9, the water content of the sandy mudstone and the water content rate at different stages can be calculated by the processing unit, so that the change of the water content of the sandy mudstone can be effectively monitored.

[0060] Furthermore, the positive pressure chamber 6 and the negative pressure chamber 7 are respectively connected to the mist outlet of the humidifier 12 and the air inlet 16 of the vacuum pump 14 through the pressure stabilizing and balancing port 8. The pressure stabilizing and balancing port 8 is used as a transitional connecting pipe body to connect the humidifier and other components together to ensure that the gas and liquid between the various components can be smoothly transmitted to balance the pressure inside the system and balance the air pressure.

[0061] Furthermore, the air inlet 16 of the vacuum pump 14 is provided with a stop valve 18, which can effectively prevent gas from flowing back when the vacuum pump stops working or the system pressure fluctuates, thereby maintaining the vacuum degree or low pressure state in the system.

[0062] Furthermore, a temperature lock cover 3 is provided on the wide temperature range thermostatic box 1, and the temperature lock cover 3 is provided with a handle 4 for convenient opening and closing.

[0063] Furthermore, a support platform 11 is provided at the bottom of the wide temperature range constant temperature box 1, a buffer layer is provided on the top of the support platform 11, and the electronic gravity sensor 9 is installed on the top of the buffer layer.

[0064] Furthermore, a gravity sensing protective cabin 10 is arranged around the electronic gravity sensor 9. The gravity sensing protective cabin 10 is designed as a sealed structure as a whole. The edges of each layer of material are sealed with sealant or special sealing technology to prevent dust, moisture or other impurities from entering the cabin and damaging the electronic gravity sensor. The innermost layer is made of rubber shock-absorbing material, which can effectively absorb the vibration energy transmitted to the protective cabin from the outside world; the middle layer is an anti-interference material, which uses a metal shielding net, which can prevent external electromagnetic interference signals from affecting the normal operation of the electronic gravity sensor by reflecting and absorbing electromagnetic waves, ensuring the accuracy of its measurement data; the outermost layer uses high-temperature and low-temperature resistant materials, and uses ceramic fiber composite materials, which can maintain stable physical and chemical properties in a wide temperature range environment, protect the internal sensor and other materials from being affected by temperature changes, and maintain the overall structural integrity of the protective cabin.

[0065] As an implementation method, in this embodiment, the outer shell material of the wide temperature range thermostatic box 1 is made of stainless steel, the insulation layer material is made of polyurethane material, and the liner material is made of aluminum alloy. A high-precision temperature sensor is installed in the thermostatic box to monitor the temperature in the box in real time. The sensor transmits the temperature signal to the control system, and the control system compares the preset temperature value with the actual monitored temperature. When the temperature deviates from the set value, the control system will start the heating or cooling device for adjustment.

[0066] As an implementation method, in this embodiment, the heating device in the temperature control device 2 adopts an electric heating method, which converts electrical energy into thermal energy. Its power can be selected and adjusted according to the size of the box and the required heating rate. The refrigeration system is based on the compressor refrigeration principle, and the heat transfer and temperature reduction are achieved through the circulation of refrigerant in the evaporator, condenser and other components. Advanced refrigeration systems can achieve efficient refrigeration in a wide temperature range and have good temperature stability and rapid response capabilities. A circulating fan is installed in the box to promote the circulation of air in the box. Reasonable air duct design ensures that the air in the box can be evenly distributed to avoid local over-high or over-low temperatures.

[0067] As an implementation method, in this embodiment, the temperature lock cover plate 3 is made of polyurethane insulation material, and there are a large number of tiny pore structures inside it, which greatly increases the thermal resistance of heat transfer, further reduces the heat transfer rate through the temperature lock cover plate, enhances the insulation effect, helps to maintain the constant temperature inside the device, and improves the experimental accuracy; the vacuum pump 14 closes the temperature lock cover plate 3 when it is working to prevent the imbalance of air pressure inside and outside the box. When the vacuum pump 14 is working, the temperature lock cover plate 3 is in a closed state, but it can still achieve constant temperature during the test process. This mainly depends on the ventilation system integrated in the temperature control device. The ventilation system is carefully designed and closely connected to the internal environment of the wide temperature range constant temperature box 1. When the vacuum pump 14 is running, the gas pressure and composition in the box will change. At this time, the ventilation system can accurately monitor these changes and dynamically adjust according to the preset temperature and gas concentration parameters. It ensures that while maintaining the stable pressure in the box, the impact of heat or gas composition changes caused by the operation of the vacuum pump is minimized through efficient gas circulation and heat exchange mechanisms. Even when the vacuum pump is running continuously, the ventilation system can continue to provide a stable temperature environment in the constant temperature box, so that the temperature in the box is always kept within the set range, thereby ensuring that the entire test process is not affected by temperature fluctuations and ensuring the accuracy and reliability of the experimental results.

[0068] As an implementation method, in this embodiment, the humidifier 12 and the vacuum pump 14 are respectively installed on the top of the electromechanical equipment protection pad 13. The electromechanical equipment protection pad 13 is made of a composite of multiple layers of materials. The top layer is made of rubber material with certain elasticity and wear resistance. Its function is to directly contact the bottom of the electromechanical equipment, provide a soft support surface, reduce the friction and hard contact between the equipment and the pad, and prevent the bottom of the equipment from being scratched or worn during operation. The middle layer is made of fiber material with good shock absorbing properties, which is mainly responsible for absorbing and dispersing the vibration energy generated by the operation of the electromechanical equipment. The bottom layer is a high-strength plastic plate with high strength and stability. Its purpose is to provide a stable support foundation for the entire protection pad, to ensure that the pad will not be excessively deformed or displaced when bearing the weight and vibration of the equipment, and to produce a buffering effect when the equipment is running, reducing the impact of vibration and shock on the equipment.

[0069] A method for using a sandy mudstone moisture content control device based on the positive and negative pressure principle comprises the following steps:

[0070] S1: Install the moisture content control unit in the wide temperature range constant temperature box 1;

[0071] S2: Check the air tightness of each component of the moisture content control unit, and check whether the temperature control device 2, the electronic gravity sensor 9, the humidifier 12 and the rotary vacuum pump 14 are working properly;

[0072] S3: Open the wide temperature range thermostatic box 1, and place the sandy mudstone sample 21 in the mounting groove 5a on the sample fixing table 5;

[0073] S4: According to different working conditions of sandy mudstone, the wide temperature range thermostat 1 is closed, and the temperature in the wide temperature range thermostat 1 is adjusted by the temperature control device 2. The electronic gravity sensor 9 is connected to the calculation and data processing unit to collect and transmit sandy mudstone data, and the initial mass of the sandy mudstone is recorded as m;

[0074] S5: The temperature in the wide temperature range constant temperature box 1 is controlled at room temperature by the temperature control device 2, and the sandy mudstone on the sample fixing table 5 is air-dried until the data recorded by the electronic gravity sensor 9 does not change, that is, the sandy mudstone has been completely air-dried, and its mass is recorded as m0. The humidifier 12 and the vacuum pump 14 are started to allow water vapor to enter the negative pressure chamber 7 from the positive pressure chamber 6 through the pores of the sandy mudstone in the sample fixing table 5, so that the water content of the sandy mudstone increases. After positive pressure humidification, negative pressure assisted water vapor penetration and other operations, the total mass of the sandy mudstone and the water contained inside at a certain moment is m t , the mass of water mw = m t -m0, the moisture content ω is calculated as:

[0075]

[0076] The initial gravity G0 of the sandy mudstone sample was measured by an electronic gravity sensor (9) before the experiment. According to the gravity calculation formula G=mg, we can get At a certain measuring moment after the positive and negative pressures and the humidification process are completed, the electronic gravity sensor 9 measures the total gravity G of the sandy mudstone and the water contained in it. t , we can get mt = Gt / g, and replace m0 and m t Substituting the expression into the moisture content calculation formula, we can get:

[0077]

[0078] In this way, the real-time measured data of the electronic gravity sensor (9) and the computing and data processing unit are directly used to calculate the water content and rate of sandy mudstone at different stages in real time.

[0079] Assume that ω1 is the water content of sandy mudstone at time t1, and ω2 is the water content of sandy mudstone at time t2, then:

[0080]

[0081] The rate of change of moisture content v can be expressed as:

[0082]

[0083] Substituting the expressions of ω1 and ω2 into the equation, we get:

[0084]

[0085] After simplification, we get:

[0086]

[0087] Measured by gravity sensor, let G0 be the gravity corresponding to the dry weight of sandy mudstone, G t1 is the total gravity of sandy mudstone and the water contained in it at that moment, G t2 is the total gravity of sandy mudstone and the water contained inside at the moment, then the expression of water content change rate v is:

[0088]

[0089] A method for controlling the moisture content and its changing rate of a sandy mudstone moisture content control device based on the positive and negative pressure principle comprises the following steps:

[0090] By adjusting the humidification amount of the humidifier 12 and the pressure in the positive pressure chamber 6, the amount of water vapor entering the pores of the sandy mudstone can be accurately controlled. According to the pore structure and target moisture content of the sandy mudstone, the working power of the humidifier 12 and the pressure value of the positive pressure chamber 6 are set. For sandy mudstone with smaller pores, the humidification amount is appropriately reduced and the positive pressure is increased, so that the water vapor can slowly and fully penetrate into the pores, avoiding pore blockage or uneven moisture distribution due to excessive and rapid water vapor.

[0091] The moisture absorption curves of different types of sandy mudstones under different positive pressures and humidification amounts are determined through preliminary experiments. Based on this, the positive pressure humidification process is accurately controlled in the formal experiment, thereby achieving effective control of the increase in moisture content. The air inlet 16 of the vacuum pump 14 is connected to the negative pressure chamber 7. By adjusting the suction rate of the vacuum pump 14 and the pressure in the negative pressure chamber 7, the migration speed and discharge amount of water vapor in the sandy mudstone are controlled. When it is necessary to accelerate the penetration of moisture, the suction power of the vacuum pump 14 is increased to enhance the negative pressure effect, so that the moisture can flow from the positive pressure chamber 6 to the negative pressure chamber 7 through the pores of the sandy mudstone faster under the drive of the pressure difference, ensuring that the rock is fully moistened and the moisture is evenly distributed, while avoiding moisture residue, thereby improving the accuracy and integrity of moisture content measurement.

[0092] The wide temperature range thermostat 1 is connected to the external temperature control device 2, and the temperature can be accurately controlled at different stages; in the air-drying stage, the temperature is controlled in an appropriate range slightly higher than the room temperature to accelerate the evaporation of water, so that the sandy mudstone reaches a completely air-dried state as soon as possible, and the dry weight m0 is accurately obtained. In the water content increase stage, the appropriate temperature is selected according to the characteristics of the sandy mudstone and the target water content. For some sandy mudstones whose water absorption is enhanced at higher temperatures, the temperature can be appropriately increased to promote water absorption, but it is necessary to avoid excessively high temperatures that cause changes in the internal structure or mineral composition of the rock; through precise temperature regulation and auxiliary positive and negative pressure effects, effective control of the water content is achieved;

[0093] The electronic gravity sensor 9 under the sample fixing table 5 monitors the mass change of sandy mudstone in real time and transmits it to the calculation and data processing unit. During the experiment, the real-time water content ω and the water content v change rate are calculated according to the gravity change, and the gravity data is recorded at a certain time interval. Once the water content change rate is found to deviate from the expected range, the positive pressure, negative pressure or temperature parameters can be adjusted in time; when the calculated water content or the water content change rate does not match the preset value, the system automatically adjusts the working parameters of the humidifier 12, vacuum pump 14 or temperature control device 2; if the water content increases too fast, reduce the humidification amount of the humidifier or reduce the positive pressure cabin pressure; if the water content increases too slowly, appropriately increase the vacuum pump exhaust power or increase the temperature. Through this real-time monitoring and feedback adjustment mechanism, the water content change rate can be accurately controlled to ensure that the water content of sandy mudstone changes at a predetermined rate to meet the test or engineering requirements.

Claims

1. A device for controlling the moisture content of sandy mudstone based on the principle of positive and negative pressure, characterized in that: It comprises a wide temperature range constant temperature box (1) and a temperature control device (2); A moisture content control unit is installed in the wide temperature range constant temperature box (1), and the moisture content control unit includes a sample fixing table (5), and the sample fixing table (5) is provided with a mounting groove (5a) adapted to the shape of the sandy mudstone sample (21), and the mounting groove (5a) is respectively connected with the positive pressure cabin (6) and the negative pressure cabin (7) provided on both sides of the sample fixing table (5), the positive pressure cabin (6) is connected to the mist outlet of the humidifier (12), and the negative pressure cabin (7) is connected to the air inlet (16) of the vacuum pump (14), and the sample fixing table (5), the positive pressure cabin (6) and the negative pressure cabin (7) are provided with a sealing cover plate (20) on the top, and an electronic gravity sensor (9) is provided below the sample fixing table (5), and the electronic gravity sensor (9) is connected to the calculation and data processing unit; The temperature control device (2) is installed on the wide temperature range constant temperature box (1) and is used to adjust the temperature inside the wide temperature range constant temperature box (1).

2. The device for controlling the moisture content of sandy mudstone based on the positive and negative pressure principle according to claim 1 is characterized in that: The positive pressure chamber (6) and the negative pressure chamber (7) are respectively connected to the mist outlet of the humidifier (12) and the air inlet (16) of the vacuum pump (14) through the pressure stabilizing and balancing port (8).

3. The device for controlling the moisture content of sandy mudstone based on the positive and negative pressure principle according to claim 2 is characterized in that: The air inlet (16) of the vacuum pump (14) is provided with an air stop valve (18).

4. The device for controlling the moisture content of sandy mudstone based on the positive and negative pressure principle according to claim 1 is characterized in that: The wide temperature range thermostatic box (1) is provided with a temperature lock cover (3), and the temperature lock cover (3) is equipped with a handle (4) for easy opening and closing.

5. The device for controlling the moisture content of sandy mudstone based on the positive and negative pressure principle according to claim 1 is characterized in that: A support platform (11) is provided at the bottom of the wide temperature range constant temperature box (1), a buffer layer is provided on the top of the support platform (11), and the electronic gravity sensor (9) is installed on the top of the buffer layer.

6. The method for using the sandy mudstone moisture content control device based on the positive and negative pressure principle according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Install the moisture content control unit in the wide temperature range constant temperature box (1); S2: Check the air tightness of each component of the moisture content control unit, and check whether the temperature control device (2), the electronic gravity sensor (9), the humidifier (12) and the rotary vacuum pump (14) are working properly; S3: Open the wide temperature range thermostatic box (1), and place the sandy mudstone sample (21) in the mounting groove (5a) on the sample fixing table (5); S4: according to different working conditions of sandy mudstone, the wide temperature range constant temperature box (1) is closed, the temperature in the wide temperature range constant temperature box (1) is adjusted by the temperature control device (2), the electronic gravity sensor (9) is connected to the calculation and data processing unit, the sandy mudstone data is collected and transmitted, and the initial mass of the sandy mudstone is recorded as m; S5: The temperature in the wide temperature range thermostat (1) is controlled at room temperature by the temperature control device (2), and the sandy mudstone on the sample fixing table (5) is air-dried until the data recorded by the electronic gravity sensor (9) does not change, that is, the sandy mudstone has been completely air-dried, and its mass is recorded as m0. The humidifier (12) and the vacuum pump (14) are started to allow water vapor to pass from the positive pressure chamber (6) through the pores of the sandy mudstone in the sample fixing table (5) into the negative pressure chamber (7), so that the water content of the sandy mudstone increases. After positive pressure humidification, negative pressure assisted water vapor penetration and other operations, the total mass of the sandy mudstone and the water contained in it at a certain moment is m t , the mass of water mw = m t -m0, the moisture content ω is calculated as: The initial gravity G0 of the sandy mudstone sample was measured by an electronic gravity sensor (9) before the experiment. According to the gravity calculation formula G=mg, we can get At a certain measuring moment after the positive and negative pressures and the humidification process are completed, the electronic gravity sensor (9) measures the total gravity G of the sandy mudstone and the water contained in it. t , we can get mt = Gt / g, and replace m0 and m t Substituting the expression into the moisture content calculation formula, we can get: In this way, the real-time measured data of the electronic gravity sensor (9) and the computing and data processing unit are directly used to calculate the water content and rate of sandy mudstone at different stages in real time. Assume that ω1 is the water content of sandy mudstone at time t1, and ω2 is the water content of sandy mudstone at time t2, then: The rate of change of moisture content v can be expressed as: Substituting the expressions of ω1 and ω2 into the equation, we get: After simplification, we get: Measured by gravity sensor, let G0 be the gravity corresponding to the dry weight of sandy mudstone, G t1 is the total gravity of sandy mudstone and the water contained in it at that moment, G t2 is the total gravity of sandy mudstone and the water contained in it at the moment, then the expression of water content change rate v is:

7. The method for controlling the water content and its changing rate of the sandy mudstone water content control device based on the positive and negative pressure principle according to any one of claims 1 to 5, characterized in that: The following steps are involved: By adjusting the humidification amount of the humidifier (12) and the pressure in the positive pressure chamber (6), the amount of water vapor entering the pores of the sandy mudstone is controlled. According to the pore structure and target water content of the sandy mudstone, the working power of the humidifier (12) and the pressure value of the positive pressure chamber (6) are set. For sandy mudstone with smaller pores, the humidification amount is appropriately reduced and the positive pressure is increased, so that the water vapor can slowly and fully penetrate into the pores, thereby avoiding pore blockage or uneven water distribution due to excessive and rapid water vapor. The moisture absorption curves of different types of sandy mudstone under different positive pressures and humidification amounts are determined through preliminary experiments, and based on this, the positive pressure humidification process is controlled in the formal experiment, thereby achieving effective control of the increase in water content. The air inlet (16) of the vacuum pump (14) is connected to the negative pressure chamber (7), and the migration speed and discharge amount of water vapor in the sandy mudstone are controlled by adjusting the suction rate of the vacuum pump (14) and the pressure in the negative pressure chamber (7). When it is necessary to accelerate the penetration of water, the suction power of the vacuum pump (14) is increased to enhance the negative pressure effect, so that the water flows faster from the positive pressure chamber (6) to the negative pressure chamber (7) through the pores of the sandy mudstone driven by the pressure difference, ensuring that the rock is fully moistened and the water content is evenly distributed, while avoiding water residue, thereby improving the accuracy and integrity of the water content measurement; The wide temperature range thermostat (1) is connected to the external temperature control device (2) to accurately control the temperature at different stages. In the air-drying stage, the temperature is controlled within an appropriate range slightly higher than the room temperature to accelerate the evaporation of water, so that the sandy mudstone reaches a completely air-dried state as soon as possible and the dry weight m0 is accurately obtained. In the water content increasing stage, the appropriate temperature is selected according to the characteristics of the sandy mudstone and the target water content. For some sandy mudstones whose water absorption is enhanced at higher temperatures, the temperature can be appropriately increased to promote water absorption, but it is necessary to avoid excessively high temperatures that may cause changes in the internal structure or mineral composition of the rock. Through precise temperature control and the assistance of positive and negative pressure effects, effective control of the water content is achieved. The electronic gravity sensor (9) below the sample fixing table (5) monitors the mass change of the sandy mudstone in real time and transmits it to the calculation and data processing unit. During the experiment, the real-time water content ω and the water content v change rate are calculated according to the gravity change, and the gravity data is recorded at a certain time interval. Once it is found that the water content change rate deviates from the expected range, the positive pressure, negative pressure or temperature parameters are adjusted in time; when the calculated water content or the water content change rate does not match the preset value, the control system automatically adjusts the working parameters of the humidifier (12), vacuum pump (14) or temperature control device (2); if the water content increases too fast, the humidification amount of the humidifier is reduced or the positive pressure cabin pressure is reduced; if the water content increases too slowly, the vacuum pump exhaust power is appropriately increased or the temperature is increased.

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